Bonded arc welding flux and liquid binding agent therefor

ABSTRACT

Arc welding flux comprising finely divided flux material and a binding agent, the binding agent comprising finely divided water soluble or water dispersible material of the class consisting of fluorides, mixed fluoride, aluminates, hydroxides and carbonates of the alkali metals, at least one additional material of said class being present when said aluminate is present, said binding agent being present when said aluminate is present, said binding agent being present in quantity at least sufficient to provide adequate bond strength in the welding flux after the flux material, binding agent and water have been intensively mixed, dried and baked at from 650* F.

United States Patent [1 1 DeLong et a1.

[ Oct. 30, 1973 BONDED ARC WELDING FLUX AND LIQUID BINDING AGENTTIIEREFUR 22 Filed: on. 13,1970

21 Appl. No.: 80,507

[52] US. Cl 148/26, 148/23, 219/73, 219/137, 219/146 [51] Int. Cl. C23el/08 [58] Field of Search 148/26, 23; 106/313 [56] References CitedUNITED STATES PATENTS 1,946,958 2/1934 Anastasiadis 148/26 X 3,501,3543/l970 DeLong 148/23 3,580,748 5/1971 DeLong, 148/26 3,320,100 5/1967Coless 148/26 Primary Examiner-G. T. Ozaki Attorney-Edward l-loopes [57]ABSTRACT Arc welding flux comprising finely divided flux material and abinding agent, the binding agent comprising finely divided water solubleor water dispersible material of the class consisting of fluorides,mixed fluoride, aluminates, hydroxides and carbonates of the alkalimetals, at least one additional material of said class being presentwhen said aluminate is present, said binding agent being present whensaid aluminate is present, said binding agent being present in quantityat least sufficient to provide adequate bond strength in the weldingflux after the flux material, binding agent and water have beenintensively mixed, dried and baked at from 650 F.

2 Claims, No Drawings BONDED ARC WELDING FLUX AND LIQUID BINDING AGENTTHEREFOR This invention relates to bonded arc welding flux; moreparticularly, it relates to a non-silicate-bonded arc welding flux withrehydration resistance equal to or better than silicate bonded fluxes ofthe prior art and a liquid binding agent therefor.

Bonded fluxes appropriate to arc welding use are compounded frompowdered flux materials such as minerals, oxides, salts and metalseither for application as coatings to covered welding electrodes or foragglomeration and use along with the electrode in the submerged arcprocess.

For over 50 years the alkali metal silicates have been without seriouscompetition as binding agents for the flux coatings applied to weldingelectrodes of the ferrous, nickel and nickel-base and copper-base types.More recently they have served as the chief binding agents foragglomerated submerged arc fluxes. Not without attractions, thesesilicate binders are convenient to use and store. They produce strong,durable electrode coatings capable of withstanding normal shipping anduse without damage and control welding behavior due to the well definedand stable cup formed by the coating on the arc end of the electrodeduring welding. However, investigators in welding have long beeninterested in having some practical alternative to the alkali metalsilicates to work with to study what new effects might be secured inslag behavior and metallurgical results without the contribution ofsilica which is always made by silicate binders and without someunacceptable contribution made by the alternative binder.

In U.S. Pat. No. 3,501,354 there is disclosed an alkali metal aluminatebonded welding flux comprising finely divided flux material and abinding agent comprising alkali metal aluminate, preferably sodiumaluminate, in an amount of from 1 to 7.5 percent of the weight of thefinely divided flux material, both calculated on a waterfree basis. Thisflux has provided welding researchers with desirable new freedom informulation, since it is not limited by the silicate binders used forfluxes in the past. However, even though such aluminate bonded weldingflux has been a step in the right direction, newer areas ofinvestigation, particularly those involving welding of high strength lowalloy steel, have given researchers reason to look for still otherbinding agents for arc welding flux, with the general aim of being ableto work with slag systems which are substantially free of both silicaand the alumina contributed by aluminate binding agents. Further, thefluxes bonded withalkali metal aluminate alone are lower in rehydrationresistance than the better silicate bonded fluxes of the prior art.

The value of reaching and holding low moisture content in welding fluxesis well known. In alkali metal aluminate bonded flux such as disclosedin the above mentioned U.S. Patent it was found that satisfactorily lowmoisture levels, in the range of those existing with the better silicatebonded fluxes, were obtainable with proper bake practices; however,rehydration rates of the aluminate bonded flux, measured by exposing thebaked flux to an atmosphere of 88 percent relative humidity at roomtemperature for predetermined intervals of time and then calculating thepercent increase in weight due to moisture pickup, were at best 3 to 4times that of the best silicate bonded fluxes. Thus, although thealuminate bonded flux was useful from an experimental standpoint itwould be at a commercial disadvantage when competing against silicatebonded fluxes.

The term flux as used herein refers both to fluxes applied to core wiresby extrusion or dipping and to fluxes agglomerated into discreteparticles for use in the submerged arc welding process.

We have now found that the use of certain novel binding agents in arcwelding flux can provide both moisture level and rehydration resistanceequal to or better than that of the better silicate bonded fluxes of theprior art. Our new approach also improves the rehydration resistance ofaluminate bonded flux to a level matching or exceeding that of silicatebonded fluxes, and enables us to formulate fluxes free of both silicaand alumina if desired.

In accordance with the invention, we provide arc welding flux comprisingfinely divided flux material and a binding agent, the binding agentcomprising. finely divided water soluble or water dispersible materialof the class consisting of fluorides, mixed fluorides, aluminates,hydroxides and carbonates of the alkali metals, at least one additionalmaterial of said class being present when said aluminate is present,said binding agent being present in quantity at least sufficient toprovide adequate bond strength in the welding flux after the fluxmaterial, binding agent and water have been intensively mixed, dried andbaked at from 650 F to 950 F.

Other details, objects and advantages of the invention will becomeapparent as the following description of certain present preferredembodiments thereof proceeds.

Generally the binding agent should be present in an amount equal to atleast 1.1 percent of the weight of the flux material after the flux hasbeen baked and at least 5 percent of the weight of the binding agentshould be selected from the group consisting of lithium fluoride andlithium hydroxide.

.The term mixed fluorides includes, for example, silicofluorides such asx sin.

In a preferred form the binding agent is present in an amount equal tofrom about 1.7 percent to about 10 percent of the weight of the fluxmaterial after the flux has been baked and at least 5 percent of theweight of the binding agent is selected from the group consisting oflithium fluoride and lithium hydroxide.

In one form of our novel flux which includes alkali metal aluminateas abinding agent, we provide arc welding flux comprising finely dividedflux material and a binding agent, the binding agent consistingessentially of the following listed components present in amounts equalto the specified weight percentages of the flux material after the fluxhas been dried and baked:

Alkali metal aluminate with a molecular ratio of alkali metal oxide toaluminum oxide between about 0.9 and 1.4 0.7 to 5% Lithium fluoride 0.4to 3% Sodium fluoride 0 to 3% Potassium fluoride O to 3% Alkali metaloxide from alkali metal hydroxide or carbonate 0 to 3% Total of above10% maximum In another form of our novel flux which is free of aluminatewe provide arc welding flux comprising finely divided flux material anda binding agent, the binding agent consisting essentially of thefollowing listed components in amounts equal to the specified weightpercentages of the flux material when the flux has been dried and baked:

It will be noted that the amounts of binding'agent contributed by thehydroxides and' carbonates arelisted herein in terms of the oxide whenthey are-referred to the dried and baked flux. This is because our workhas revealed that when the completed flux is baked attemperaturestypically in the range'of 650 F to 950 F the hydroxides lose their (OH)radical and the carbonates may lose CO thus toprovide uniformity incalculating the amounts of such binding agent components present in thefinished welding flux we consider only the oxide portion thereof whendealing with the as-baked flux.

In preparing our novel fluxes we prefer to intensively mix the bindingagent component or components, in finely divided form, with water toform a uniform aqueous mixture, mix said mixture with the dry finelydivided flux material to form a wet mix of the desired consistencyextrude the wet mix on to a core wire of desired composition oragglomerate the wet mix into particles of the desired size for use assubmerged arc welding flux, and finally dry and bake the wet flux at atemperature whichyas above indicated, is in the range of 650 F to 950 F.However, the binding agent com- Lithium fluoride 5 to 10 grams Sodiumfluoride 2 to 20 grams Potassiumfluoride 0 to 5 grams.

We further provide a somewhat similar liquid binding agent with thepotassium fluoride replaced by potassium hydroxide, consistingessentially of a uniform aqueous mixture of the following listed finelydivided ingredients in the specified weights per 100cc of water:

Sodium aluminate with a molecular ratio of sodium oxide to aluminumoxide of about 1.1 8 to 12 grams Lithium fluoride 8 to 12 grams Sodiumfluoride 17 to 23 grams Potassium hydroxide 8 to 12 grams.

We also provide an aluminate-free liquid binding agent for bonded arcwelding flux consisting essentially of a uniform aqueous mixture of thefollowing listed finely divided ingredients in the specified weights per100cc of water:

Lithium hydroxide 2 to 8 grams Sodium fluoride 15 to 25 grams Sodiumhydroxide 2 to 8 grams Potassium hydroxide,- 2 to 8 grams.

The amount of any of our above described liquid binding agents necessaryto provide the properconsistency for extrusion or agglomeration andsufficient bond strength when mixed with the flux materials will varydepending on the specific flux materials used and their particle sizedistribution, as is well known in the art. However, we have found thatwith flux material mixtures typical of those presently extant in the arcwelding field the amount of liquid binding agent will be such as toprovide an amount of binding agent in the baked flux equal to betweenabout 1.1 percent and 10 ponents may also be mixed in the dry state withthe flux material and water added to and intensively mixed with theresultant dry mixturebThe main requirement in either case is to arriveat a uniform and intimate mixture of the binding agent with thefiuxmaterials, because unless such a mixture is obtained the necessary bondand other properties of the finished flux will not be secured. Thus inthe first case the binding agent and watermay be mixed by means of ahigh speed blender, and in the second case the binding agent and fluxmaterial may preferably be mixed with water in a blender such, forexample, as the P-K Twin-Cone Liquid-Solids Blender with lntensifier Barmanufactured by the Patterson-Kelly Company.

' For use in theabove-described preferred method of preparing our flux,we provide a liquid binding'agent for bonded arc welding flux consistingessentially of a uniform aqueous mixture of the following listed finelydivided ingredients in the specified weights per 100cc of water: v

Alkali metal aluminate of the classcons'istingof sodium aluminate andpotassium aluminate 5 to 40 grams v Lithium fluoride 3to 30 grams rMaterial of the class consisting of sodium fluoride and potassiumfluoride 2 to 25 grams. 1 In a preferred form this binding agentconsists essentially of a uniform aqueous mixture of the followinglisted finely divided ingredients in the specified weights per 100cc ofwater:

Sodium aluminate having a molecular ratio of sodium oxide to aluminumoxide of about 1.1 10 to-20 grams percent of the weight of the fluxmaterial present.

We have found that to be effective in our novel flux the finely dividedbinding agent components must be water soluble or water dispersible i.e.able to form at least a substantially colloidal suspension whenintensively mixed with water. This requirement insures that the bindingagent can be uniformly distributed throughout the flux material, whetheradded to the flux material as an aqueous mixture, which may be partlytrue solution and partly colloidal in character, or added in the finelydivided dry form with subsequent water addition.

For optimum rehydration resistance in the finished flux, at least 5percent of the weight of the binding agent should be lithium fluorideand/or lithium hydroxide. These lithium compounds have a much strongereffect on the rehydration resistance of the finished flux than do theother binding agent components.

One form of lithium fluoride which we have found satisfactory for use isa commercial grade material consisting of 99.5% minimum UP and having'aparticle size distribution of 100% through U. S. 100 mesh and typicallythrough U. S. 325 mesh. This material as purchased is fluffy and tendsto agglomerate into small spherical balls whenever it is mixed in thedry state, so

that special care must be taken to insure that it is intimately anduniformly dispersed throughout the flux material when using it as abinding agent component.

One form of lithium hydroxide which we have found satisfactory is acommercial grade of lithium hydroxide monohydrate, typically 57% LiOH,in the form of crystals sized to approximately 20Xl00 U. S. mesh. Thismaterial can be readily dispersed in water.

Lithium fluoride With respect to the other binding agent componentswhich we have found useful in the preferred method of preparing ourflux, the following are brief descriptions thereof:

Sodium aluminate Commercial low-priced white granular sodium aluminatetrihydrate, water soluble, containing about 40% A1 0 31% Na O, 23% waterand minor impurities. The Na O to A1 0 molecular ratio of this aluminateis about 1.1 and it readily forms a uniform liquid when mixed withwater.

Sodium fluoride Technical grade, fine powder, 99% min NaF.

Potassium fluoride Commercial grade, fine flake, 95% min KF.

Sodium hydroxide Technical 98% min NaOH.

Potassium hydroxide Technical grade, fine flake, 90% min KOH.

Lithium carbonate Technical grade, fine powder, 97% min Li,CO

Sodium carbonate Technical grade, fine powder, 99% min Na CO Potassiumcarbonate Technical grade, powder, 99% min K CO Potassium silicofluorideCommercial grade, powder, 99% typical K SiF,,.

One liquid binding agent which we have found useful in the preparationof welding flux for covered electrode use consists of, per 100cc ofwater: sodium aluminate grams, lithium fluoride 8 grams, sodium fluoride3 grams, sodium chromate 0.3 grams. This combination is mixed in a highspeed electric blender for a few minutes until a uniform liquid isobtained, after which it is added to and mixed with the flux materialsof the electrode coating formulation to form a paste satisfactory forextrusion onto the core wire. As shown in this example, we may add arust inhibitor such as sodium chromate to the liquid mixture to minimizecorrosive attack on the processing equipment or metal powders in theflux mixture; we'may also add some organic material such as sodiumcarboxymethylce'llulose (sodium CMC) to thicken the'binder and aid inmaintaining uniformity of the dispersion of the binding agentcomponents. Both such additions are well understood by those skilled inthe art and form no part of our invention.

Another liquid binding agent which we may use in welding flux forcovered electrodes consists of, per 100cc of water: sodium aluminate 15grams, lithium fluoride 6 grams, sodium fluoride 3 grams, potassiumfluoride 3 grams, sodiumchromate 0.3 grams.

From the standpoint of as-baked moisture level and rehydration rate thebest silicate bonded electrodes of which we are aware show moisturelevels in the range 0.06% to 0.12% as measured in the so-called Navywater test, which consists of fusing a crushed sample of the bakedelectrode coating in a stream of oxygen at l,800 F, and a rehydrationrate in an 88% relative hugrade, fine flake,

midity atmosphere at room temperature of about 0.15% and 0.30% afterland 6-hour exposures respectively. It should be borne in mind that thelarge preponderance of silicate fluxes on the market at present arehigher than this in rehydration rate. These figures were used asstandards of comparison for a series of experi mental covered electrodescoated with our new flux. In preparing each experiment of the series thefollowing listed finely divided flux materials in the amounts 1595 gramsThe above listed constant flux material base is typical of those used inhigh strength lime-fluoride low hydrogen electrode coatings.

Table 1 lists the compositions of eight different liquid binding agents,each of which was added to one formula weight (1,595 grams) of the abovelisted dry flux materials. Note that Experiment No. 060 utilized onlysodium aluminate; this experiment was included so that a comparisoncould be made between flux as described in the above referred to U. S.Pat. No. 3,501,354, and our novel flux. Each binding agent was preparedby adding the listed ingredients and sodium chromate to water in theproportions indicated and mixing the combination by means of a highspeed electric blender for several minutes until a uniform liquid wasobtained. A sufficient amount of the uniform liquid was then added tothe dry flux material mixture to produce a dough of suitable consistencywhich was extruded onto mild steel core wire. Table 1 lists the amountof binder liquid required to produce the proper consistency with the drymaterial mixture for each of the binders studied.

Samples of each of the electrodes were baked at 800 F for 2 hours; sucha bake is typical of those used with silicate bonded low hydrogenfluxes. Table 2 lists the amount of each binding agent component presentin each as-baked flux as a percentage of the flux material I weight.

After baking, each flux sample was checked for moisture by the Navywater test and for rehydration after 1- and 6-hour exposures to anatmosphere of 88 percent relative humidity at room temperature. Table 3lists the results of the moisture and rehydration rate checks on thefluxes studied, and for comparison lists the same data for the bestsilicate bonded flux of which we are aware.

TABLE l.LIQUID BINDING AGENT COMPOSITIONS Experiment No.

Binding agent component 060 066 080 081 037 085 071 086 H O l00cc.....cc.-.... l00cc..... 100cc..... 100cc. Sodium chromate .3g. Sodiumaluminate trihydrate (40% A1 0 31% Na- O, 15g 15g 10g...

Lithium hydroxide monohydrate... Sodium fluoride... Potassium fluorideSodium hydroxide fetea yl lhxs edqst- TABLE l.-L1QU1D INDTNEAGENTCOMPOSITIONS-Continued ExperimentNo.

Binding agent component 060 066 Sodium carbonate......

Potassium carbonate...

Potassium silicofluoride Wt. of liquid binding agent used per 1595g flmaterial.

"' TABLE 2.-BINDING AGENT CONTENT OF'BAKED FLUX, PERCENT* Experiment No.

Binding agent component 060 066 080 081 037 085 07] 086 Sodium aluminateLithium fluoride Lithium oxide (from LiOH H Sodium fluoride Potassiumfluoride Sodium oxide (from NaOH) .5 Potassium oxide (from KOH)... 1.0.5 .5 1.2 .5 Sodium oxide (from Na CO -.4 Potassium oxide (from K- CO eass ymsilieqfli risl .4 Total binding agent a 4.5 Percent of bindingagent weight comprising UP 0 46 28 23 6 19.5 11 0 and/or L120.

, Wt. binding agent component X 00 Flux material wt. (=1595g) TABLE3.MO1STURE CONTENT AND REHYDRATION RATE OF FLUXES'KF'TE'REWF BAKE FOR 2HOURS Best Experiment No. silicate bound 060 066 080 081 037. 085 071086 flux Percent moisture by Navy Water Test .075 .074 .073 .064 .063.068 .072 .087 .06.l2 Percent H O picked up after 1 hr at room temp. in88% .51 .17 .14 .10 .06 .11 .26 .40 .15

relative humidity. v Percent H O picked up after 6 hr room temp. in 88%rela- 1.82 .40 .40 .28 .14 .28 .40 .77 .30

tive humidity.

Several advantages and features of our flux and bindelectrodes andembody the use of a uniform liquid ing agent are apparent from the dataset forth in the tabinding agent which is then added to the dry fluxmatebles. First, comparing Experiment Nos. 060 and 066, it rial, it willbe appreciated that the principles are appliwill be seen that theaddition of lithium fluoride in the 40 cable to other types of fluxesand other means of addquantity shown reduced the rehydration rate of theflux i th bindin ent to th flux s. For xample, in the y a factor ofthree after 1 how's exposure and y a preparation of agglomeratedsubmerged arc fluxes we factor of approximately four after-6 hoursexposure, as may add h a di id d bi di agent to h d compared, to lherehydration rate of the flux bonded mixture of flux materials andthereafter add water to with aluminate alone. The additional use ofsodium fluh d mix in a blender such as the Patterson-Kelly Q P- and theeombihatloh of Sodium Twin-Cone Liquid-Solids Blender above referred to.and Potassium hydroxide P- reduced the The high speed intensifier bar inthe Patterson-Kelly rehydratioh rate of the h somewhat furtherblenderprevents lithium fluoride if used from balling three experimentsembodying our hovel flux and bind up" and assures satisfactoryuniformity of dispersion.

ihghgeht including eli n t (066 080 and 081), the Mixing is continueduntil the desired agglomeration has moisture level and rehydration rateof the baked flux occurred ft which the fl is removed from the werecomparable with that of the best silicate bonded mixer, dried baked andthen screened through f flux. The remaining four experiments werealuminate ample a 20 mesh screeh to id a abl free Experiments and 071Show that we-are glomerated flux. In any case, it is imperative thatintenable to secure excellent moisture level and rehydration Sivablending be carried out so h proper bond rate in Such h a flux n a inone of h" strength canbe developed in the binding agent. preferredbinding agent components lithium fluoride or Recapitmatihg, wa id arcldi flux hi h lithium hydroxide. Experiment 086 contains no lithium mayb f f ili d l may b f f l i g p h l h d 8;"; p g g if desired, and whichis characterized by moisture level i e molstule eve ah Te 3' ration rate9 t is are and rehydration rate after a normal bake in the ran esomewhat superior to that of Experiment 060 contain- 650 F to 950 Fcomparable to or better h h i g a m t f not as g as the P ture level andrehydration rate of the best silicatemehts cohtfhhlhg e hthlumcompouhdswe P e bonded fluxes of the prior art. Consequently, researchtouse llthl m fluoride an hydroxide as bmdmg ers now have freedom to studythe effect of flux which agent components In amount equal t M16851 5Percent 15 free of both silica and alumina and which, moreover, of thetotal weight. of the binding agent. is competitive with commercialsilicate bonded fluxes While the above described examples haveparticular in the critical areas of moisture level and rehydrationreference to welding flux for application to covered rate.

The liquid binding agent for bonded arc welding flux herein disclosed isclaimed in our copending divisional application Ser. No. 210,144, filedDec. 20, 1971 now US. Pat. No. 3,704,149.

While we have described certain present preferred embodiments of theinvention it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied within the scopeof the following claims.

We claim:

1. Are welding flux comprising finely divided flux material and abinding agent, the binding agent consisting essentially of the followinglisted components present in amounts equal to the specified weightpercentages of the flux material after the flux has been dried andbaked:

Alkali metal aluminate with a molecular ratio of alkali metal oxide toaluminum oxide Lithium fluoride 0.4 to 3% Sodium fluoride to 3%Potassium fluoride 0 to 3% Alkali metal oxide from alkali metalhydroxide or carbonate 0 to 3% Total of above maximum 2. Are weldingflux comprising finely divided flux material and a binding agentconsisting essentially of the following listed components in amountsequal to the specified weight percentages of the flux material after theflux has been dried and baked:

Lithium fluoride 0 to 2% Sodium fluoride 0 to 4% Potassium fluoride 0 to3% Lithium oxide from lithium hydroxide 0 to 3% Sodium oxide from sodiumhydroxide 0 to 3% Sodium oxide from sodium carbonate 0 to 2% Potassiumoxide from potassium hydroxide 0 to 3% Potassium oxide from potassiumcarbonate 0 to 2% Potassium silicofluoride 0 to l% Total of above [.1 to10%.

UNITED STATES PATENT OFFICE CERTIFICATE OF QORECTION Patent No. 3 769099 Dated October 30, 1973 William T. DeLong, Edwin R. Szumachowski andInventor(s) Harold R. Heverly It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the caption, after the names and addresses of the inventors insert:-Assignee: Teledyne Inc., Los Angeles, California, a corporation ofDelaware.---.

Signed and sealed this 2nd day of April 197M.

(SEAL) Atte st:

EDWARD MJ IETCHERJR. G. MARSHALL DANN Attesting Officer Commissioner ofPatents ORM PO-1 050 (1 O69) USCOMM-DC 60376P69 fi' U.S. GOVERNMENTPRINTING OFFICE: 1969 O-366-384.

UNITED STATES PATENT OFFICE CERTIFICATE OF QORRECTION Patent No.3.769,099 Dated October 30, 1973 William T. DeLong, Edwin R.Szumachowski and Inventor(s) Harold R. Heverly It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the caption, after the names and addresses of the inventors insert:--Assignee: Teledyne Inc., Los Angeles, California, a corporation ofDelaware.-.

Signed and sealed this 2nd day of April 197b,.

(SEAL) Atte st:

EDWARD M.FIETGHER,JR. C. MARSHALL DA'NN Attesting Officer Commissionerof Patents )RM PO-105O 10-69 USCOMM-DC 60376-P69 3% us GOVERNMENTPRINTING OFFICE 1909 0-366-884.

2. Arc welding flux comprising finely divided flux material and abinding agent consisting essentially of the following listed componentsin amounts equal to the specified weight percentages of the fluxmaterial after the flux has been dried and baked: Lithium fluoride 0 to2% Sodium fluoride 0 to 4% Potassium fluoride 0 to 3% Lithium oxide fromlithium hydroxide 0 to 3% Sodium oxide from sodium hydroxide 0 to 3%Sodium oxide from sodium carbonate 0 to 2% Potassium oxide frompotassium hydroxide 0 to 3% Potassium oxide from potassium carbonate 0to 2% Potassium silicofluoride 0 to 1% Total of above 1.1 to 10%.